Injection mold cooling tube with porous insert

ABSTRACT

An injection-molding machine cooling tube, which cools molded plastic parts, includes a porous cooling tube having an outer surface and an inner surface. Preferably, the porous cooling tube has a porosity in the range of 3-20 microns. A cooling fluid passageway is preferably disposed adjacent the porous cooling tube outer surface and is configured to carry a cooling fluid to extract heat from the porous cooling tube. Fluid flow structure, preferably a vacuum, is configured to cause a molded plastic part inside the porous cooling tube to expand into contact with at least a portion of the inner surface of the porous cooling tube.

The present application is a continuation of U.S. patent applicationSer. No. 10/246,916 filed Sept. 19, 2002, now U.S. Pat. No. 6,737,007incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates, in general, to cooling tubes and isparticularly, but not exclusively, applicable to cooling tubes used in aplastic injection-molding machine to cool plastic parts, such as plasticparisons or preforms. More particularly, the present invention relatesto a structural configuration of these cooling tubes, and also to methodof manufacturing and using such tubes, for example in the context of amanufacturing process for preforms made from polyethylenetetraphthlate(PET) or the like.

2. Related Art

In order to accelerate cycle time, molding machines have evolved toinclude post mold cooling systems that operate simultaneously with theinjection molding cycle. More specifically, while one injection cycle istaking place, the post mold cooling system, typically acting in acomplementary fashion with a robotic part removal device, is operativeon an earlier formed set of molded articles that have been removed fromthe mold at a point where they are still relatively hot, butsufficiently solid to allow limited handling.

Post mold temperature conditioning (or cooling) molds, nests or tubesare well known in the art. Typically, such devices are made fromaluminum or other materials having good thermal conductivity properties.

To improve cooling efficiency and cycle time performance, EP patent 0283 644 describes a multi-position take-out plate that has a capacity tostore multiple sets of preforms for more than one injection cycle. Inother words, each set of preforms is subjected to an increased period ofaccentuated conduction cooling by retaining the preforms in the coolingtubes for more than one injection cycle. With increased cooling, thequality of the preforms is enhanced. At an appropriate point in time, aset of preforms is ejected (usually by a mechanical ejection mechanism)from the take-out plate onto a conveyor to allow a new set of preformsto be inserted into the now vacant set of cooling tubes. EP patent 0 283644 is incorporated herein by reference.

In many other cooling tube arrangements, the preform (at some point, ifnot from the point of introduction) looses contact with the internalside walls of the cooling tube, which loss of thermal contact lessenscooling efficiency and causes uneven cooling. As will be understood,uneven cooling can induce part defects, including deformation of overallshape and crystallization of the plastic (resulting in areas that arevisibly hazed). Furthermore, lack of contact can cause ovality acrossthe circumference of the preform, while the loss of the cooling effectcan mean that a preform is removed from the cooling tube at anexcessively high temperature. In addition to causing surface scratchingand overall dimensional deformation, premature removal of a preform atan overly high temperature can also result in the semi-molten exteriorof preform sticking either to the tube or another preform; all theseeffects are clearly undesirable and result in part rejection andincreased costs to the manufacturer.

European patent EP 0 266 804 describes an intimate fit cooling tube thatis held within an end-of-arm-tool (EOAT) of a robot. The intimate fitcooling tube is water cooled and is arranged to receive a preformshortly after it has attained the glass-transition temperature thatallows handling of its form without catastrophic deformation. Moreparticularly, after the preform has undergone some cooling within theclosed mold, the mold is opened, the EOAT extended between the cavityand core sides of the mold and the preform off-loaded from a core intothe cooling tube that then acts to cool the exterior of the preform by aconduction process. However, as the preform cools it will shrink andtherefore may loose contact across its entire circumference with thecooling tube yielding an uneven cooling effect.

U.S. Pat. Nos. 4,102,626 and 4,729,732 are further typical of prior artsystems in that they show a cooling tube formed with an external coolingchannel machined in the outer surface of the tube body, a sleeve is thenassembled to the body to enclose the channel and provide an enclosedsealed path for the liquid coolant to circulate around the body.

WO 97/39874 discloses a tempering mold that has circular coolingchannels included within its body. EP 0 700 770 discloses anotherconfiguration that includes an inner and outer tube assembly to formcooling channels therebetween.

U.S. Pat. No. 4,208,177 discloses an injection mold cavity containing aporous element that communicates with a cooling fluid passagewaysubjecting the cooling fluid to different pressures to vary the flow offluid through the porous plug.

U.S. Pat. No. 4,047,873 discloses an injection blow mold in which thecavity has a sintered porous sidewall that permits a vacuum to draw theparison into contact with the cooling tube sidewall.

U.S. Pat. No. 4,295,811 and U.S. Pat. No. 4,304,542 disclose aninjection blow core having a porous metal wall portion.

A “Plastics Technology Online” article entitled “Porous Molds' BigDraw”, by Mikell Knights, printed from the Internet on Jul. 27, 2002,discloses a porous tooling composite called METAPOR™. The articlediscloses the technique of polishing this material to close slightly thepores to improve the surface finish and reduce the porosity.

An article from International Mold Steel, Inc., entitled “PorousAluminum Mold Materials”, by Scott W. Hopkins, printed from the Interneton Jul. 27, 2002, also discloses porous aluminum mold materials. Thematerials and applications disclosed in the above two articles refer tovacuum thermoforming of plastics in the mold itself, in which preheatedsheets of plastic are drawn into a single mold half via a vacuum drawnthrough the porous structure of the mold half.

SUMMARY OF THE INVENTION

According to a first aspect of the present invention, structure and/orsteps are provided for a tube assembly for operating on a malleablemolded plastic part. The tube assembly comprising a porous tube having aprofiled inside surface, and a vacuum structure configured to cooperatewith the porous tube to provide, in use, a reduced pressure adjacent theinside surface. The reduced pressure causes an outside surface of themalleable molded plastic part, locatable within the tube assembly, tocontact the inside surface of the porous insert so as to allow asubstantial portion of the outside surface of the malleable part, uponcooling, to attain a profile substantially corresponding to the profileof the inside surface. In an embodiment of the invention, the poroustube is cylindrically-shaped, and the vacuum structure is provided bylocating the porous tube in a tube body and by providing at least onevacuum channel adjacent the outside surface of the porous tube, in use,for connection to a vacuum source.

The inside surface of the porous tube having an internal profile that issubstantially (if not highly and accurately toleranced to) the finaldimensions of the molded part, the porous tube of the variousembodiments of the present invention effectively causes, under cooling,a re-shaping of the molded part to its exact final shape defined by theprofile of the insert. Indeed, the reduced pressure/effective vacuumacting through the porous material essentially acts to draw themalleable preform into the final shape whilst ensuring that cooling isoptimized by continuous surface contact with a thermally efficient heatdissipation material and path.

According to a second aspect of the present invention, injection moldingmachine structure and/or steps are provided with a molding structurethat molds at least one plastic part. Furthermore, at least one porouscooling cavity is configured to hold and cool the at least one plasticpart after it has been molded by the molding structure. At least onevacuum channel is respectively configured to provide alower-than-ambient pressure to the at least one porous cavity to causethe at least one plastic part to contact the inside surface of the atleast one porous cavity.

According to a third aspect of the present invention, a method forshaping a malleable molded plastic part including the steps of: (i)receiving the molded plastic part into a porous tube; (ii) providing areduced pressure adjacent a profiled inside surface of the porous tubecausing a portion of an outside surface of the molded plastic part tomove into contact therewith and thereby attain a substantiallycorresponding shape; and (iii) extracting heat from the molded plasticpart through a heat dissipation path to solidify the molded plastic partat least to the extent required to ensure that the shape of the outsidesurface of the molded plastic part is preserved; and (iv) ejecting themolded plastic article; wherein the outer surface of the molded plasticpart is provided with a final shape that is defined by the profiledinside surface profile of the porous tube.

According to a fourth aspect of the present invention, structure and/orsteps are provided for a tube assembly for operating on a malleablemolded plastic part. The tube assembly comprising a tube body, and aporous insert located in the tube body. The porous insert includes aninside surface and an outside surface, the inside surface profiled toreflect at least a portion of the profile of the molded plastic part.The tube assembly further includes at least one vacuum channel in fluidcommunication with the porous insert. The vacuum channel configured forconnection, in use, with a vacuum source to provide a reduced pressureadjacent the inside surface to cause an outside surface of the malleablemolded plastic part, locatable within the tube assembly, to contact theinside surface so as to allow a substantial portion of the outsidesurface of the malleable part, upon cooling, to attain a profilesubstantially corresponding to the profile of the inside surface. Thetube assembly also includes a cooling structure configured forconnection, in use, with a heat dissipation path for cooling the moldedplastic part in contact with the inside surface of the porous insert.

Preferably, the porous insert has porosity in the range of about 3-20microns. A cooling fluid passageway is disposed in the tube bodyadjacent the porous insert and is configured to carry a cooling fluid toextract heat from the porous insert.

According to another aspect of the present invention, structure and/orsteps are provided for a tube assembly. The tube assembly comprising atube with an inside surface provided on a porous substrate, and a fluidflow structure. The fluid flow structure is configured to cooperate withthe porous substrate to cause, in use, a malleable molded plastic part,locatable within the tube assembly, to be drawn into contact with theinside surface so as to allow a substantial portion of an outsidesurface of the malleable part, upon cooling, to attain an outsideprofile substantially corresponding to the profile of the insidesurface.

According to an embodiment of the invention, the porous substrateincludes an inside surface and an outside surface, the inside surfaceprofiled to reflect at least a portion of the profile of the moldedplastic part; and a vacuum channel located adjacent the outer surface,the vacuum channel supporting, in use, an initial establishment of adifferential pressure from the outside surface of the porous substrateto the inside surface thereof, to induce contact, in use, between thereceived molded plastic part and the inside surface.

According to yet another aspect of the present invention, structureand/or steps are provided for an end-of-arm tool. The end-of-arm toolcomprising a carrier plate for mounting, in use, to a robot in a moldingsystem, and at least one tube assembly arranged on the carrier plate.The tube assembly is configured for receiving, in use, a molded plasticpart. The tube assembly comprising a porous tube having an insidesurface and an outside surface, the inside surface profiled to reflectat least a portion of the profile of the molded plastic part, and avacuum structure. The vacuum structure is configured to cooperate withthe porous tube to provide, in use, a reduced pressure adjacent theinside surface to cause an outside surface of a malleable molded plasticpart, locatable within the tube assembly, to contact the inside surfaceof the porous insert so as to allow a substantial portion of the outsidesurface of the malleable part, upon cooling, to attain a profilesubstantially corresponding to the profile of the inside surface.

According to a further aspect of the present invention, structure and/orsteps are provided for a molded plastic part with the shape of at leasta portion of its outside surface defined by a profiled inside surface ofa porous tube. The molded plastic part is formed by the process of: (i)receiving a malleable molded plastic part into the porous tube; (ii)reducing pressure adjacent the profiled inside surface of said poroustube causing the portion of the outside surface of the molded plasticpart to move into contact with the profiled inside surface of the poroustube, thereby to attain a shape substantially corresponding to theprofiled inside surface; and (iii) extracting heat from the moldedplastic part through a heat dissipation path to solidify the moldedplastic part sufficiently such that the outer shape of the moldedplastic part is preserved. Whereby the portion of the outside surface ofthe molded plastic part takes on a surface finish reflecting that of theprofiled inside surface of the porous insert. Preferably, the poroustube is formed of a porous substrate with the profiled inside surfacehaving interstitial spaces preferably within a range of about 3 to 20microns.

The present invention advantageously provides a cooling tube structurethat functions to cool rapidly and efficiently a just-molded plasticpart located within the cooling tube, thereby improving robustness ofthe preform and generally enhancing cycle time. Moreover, in the contextof cooling PET and the unwanted production of acid aldehyde arising fromprolonged exposure of the preform to relatively high temperatures, therapid cooling afforded by the present invention beneficially reduces therisk of the presence of unacceptably high levels of acid aldehyde in thefinished plastic product, such as a drink container. Beneficially, thepresent invention seeks to maintain a required and defined shape of themolded part, such as a preform.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments of the present invention will now be describedwith reference to the accompanying drawings, in which:

FIG. 1 is a plan view of a typical injection molding machine including arobot, and end-of-arm tool;

FIG. 2 depicts a section through a cooling tube assembly according to apreferred embodiment of the present invention;

FIG. 3 depicts a sectional, but exaggerated view, through the coolingtube assembly of the FIG. 2 embodiment, with a freshly molded part justloaded;

FIG. 4 depicts a section through the cooling tube assembly of the FIG. 2at a later point in time;

FIG. 5 depicts a section through the cooling tube assembly of analternate embodiment;

FIG. 6 depicts a view on section 5—5 of FIG. 5;

FIG. 7 depicts a section through the cooling tube assembly of a secondalternate embodiment; and

FIG. 8 depicts a section through the cooling tube assembly of a thirdalternate embodiment.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EXEMPLARY EMBODIMENTS

The present invention will now be described with respect to embodimentsin which a porous cooling tube is used in a plastic injection moldingmachine, although the present invention is equally applicable to anytechnology in which, following part formation, cooling of that part isundertaken by a cooling tube or the like. For example, the presentinvention can find application in a part transfer mechanism from aninjection molding machine and a blow-molding machine.

FIG. 1 shows a typical injection molding machine 10 capable ofco-operating with a device supporting the cooling tube of the presentinvention. During each injection cycle, the molding machine 10 producesa number of plastic preforms (or parisons) corresponding to the numberof mold cavities defined by complementary mold halves 12, 14 locatedwithin the machine 10.

The injection-molding machine 10 includes, without specific limitation,molding structure such as a fixed platen 16 and a movable platen 18. Inoperation, the movable platen 18 is moved relative to the fixed platen16 by means of stroke cylinders (not shown) or the like. Clamp force isdeveloped in the machine, as will readily be appreciated, through theuse of tie bars 20, 22 and a machine clamping mechanism (not shown) thattypically generates a mold clamp force (i.e. closure tonnage) using ahydraulic system. The mold halves 12, 14 together constitute a moldgenerally having one or more mold cavities 22, 24, with the mold halves12, 14 each located in one of the movable platen 14 and the fixed platen16. A robot 26 is provided, adjacent the fixed 16 and movable platen 14,to carry an end of arm tool (EOAT) 28, such as a take-out plate. Thetake-out plate 28 contains a number of preform cooling tubes 30 at leastcorresponding in number to the number of preforms 32 produced in eachinjection cycle, and may be a multiple thereof. In use, in a mold openposition (as shown in FIG. 1), the robot 26 moves the take-out plateinto alignment with, typically, a core side of the mold and then waitsuntil molded articles (e.g. preforms 32) are stripped from respectivecores into respectively aligned cooling tubes 30 by operation of astripper plate 33.

Cooling tubes 30 are generally shaped to reflect the external profile ofthe molded article (e.g. preform 32), so in the context of a PET preformthe cooling tubes 30 are preferably cylindrically-shaped, open-ended,hollow tubes, each having a channel at the base thereof connected to avacuum or suction unit 34 operational to draw and/or simply hold thepreforms 32 in the tubes 30.

Generally, the take-out plate 28 will be cooled either by connection toa suitable thermal sink and/or by a combination of techniques, includinginternal water channels, as will be understood.

FIG. 2 shows a cooling tube assembly 50 comprising an inner porousinsert 52 made, preferably, of a material such as porous aluminum havinga porosity in the range of about 3 to 20 microns. The porous propertiesof the substrate are generally achieved from either its materialconfiguration or a chemical removal (or adjustment) treatment process inwhich interstitial spaces are induced into the substrate, therebyproducing an internal structure that is somewhat analogous to eitherhoneycomb or a hardened sponge. The present invention can make use ofcommunicating channels through the substrate material having a sizeoutside the range of 3 to 20 microns, albeit that readily commerciallyavailable materials, such as METAPOR™ and PORCERAX™ (both manufacturedby the International Mold Steel Corporation), are discussed with respectto the preferred embodiments described herein. Porosity is, in anyevent, a function of surface finish, and machining of working of thesurface can affect porosity through the material, as will be understood.In a preferred embodiment, the inner porous insert 52 is made from astructure having definite strength and mechanically resilientproperties, although the inner porous insert could also be made fromsubstances like graphite. It is preferably that the inner porous insert52 is a thermal conductor, with it being particular preferably that thethermal conduction properties are good, e.g. a metal-based or sinteredcomposite material.

As will be understood, METAPOR™ is combination of aluminum and epoxyresin having a mix ratio of between about 65-90% aluminum powder and35-10% epoxy resin.

A typical cooling tube assembly 50 may have an internal length dimensionof about 100 millimetres (mm), with an interior diameter of about 25 mmand an outer diameter of about 40 mm, with these dimensions reflectingthe size of the molded article. Of course, tubes may be made ofdifferent diameters and lengths to suit the particular preform shapebeing cooled.

From a practical perspective, the porous insert 52 is preferably locatedin a tube body 54, which is surrounded by a sleeve 56. Cooling channels(or passageways) 58 are optionally cut or otherwise formed adjacent tothe tube body 54, and convey a cooling fluid (e.g. air, gas, or liquid)to cool the body 54 and the insert 52, thus drawing heat from the moldedplastic part in the porous insert 52. Each cooling channel preferablyconfigured to have a cross-section comprising a plurality of arcuate,elongated slots which extend around greater than 50% of a circumferenceof an inside diameter of a respective cooling cavity. Alternatively, thetube body 54 could simply be directly thermally coupled to a heat sinkto reduce a combined overall weight of the tubes and end-of-arm-tool 28,provided that the heat sink is capable of drawing sufficient heat from apreform in unit time.

Seals 60-63 between the sleeve 56 and the tube body 54 contain thecooling fluid in the grooves 4. Channels 66 are cut or otherwise formedin the exterior surface of porous insert 52 and provide a means to applya vacuum through the porous structure of the porous insert 52.

Other than the channels 66, the outer surface of the porous insert 52 isconfigured such that a good surface contact is maintained between theinsert 52 and the tube body 54, thereby to optimize heat transfer fromthe porous insert to the molded plastic part. The vacuum is appliedthrough the porous insert such that a freshly loaded molded plastic part32, shown in FIG. 3, is caused to expand in size to touch an innersurface 82 of the porous insert, as shown in FIG. 4. Thus, heat isconducted from the molded plastic part 32 to and through the porousinsert 1 to the cooled tube body 54. It is noted that the position of adome portion 80 of the preform 32 is exaggerated in FIG. 3 and that FIG.3 is representative of a time when the preform is being introduced intothe cooling tube assembly 50.

Under application of suction or vacuum, a lower-than-ambient pressure ispresent outside of insert 52, thus causing air to flow through theporous insert 52 from the inside surface 82 thereof and into channels66. This suction, in turn, causes a lower-than-ambient pressure at theouter surface of the molded plastic part, causing it to move intocontact with the inner surface 82 of the porous insert 52.

In a PET environment with a METAPOR™ insert having 3-20 microninterstitial spaces, operational vacuum pressures for the system areachievable within the range of about 10 to 30 inches of mercury (using aU3.6s Becker evacuation pump). However, it will be understood that theapplied vacuum pressure is a ultimately determined by (and is a functionof) the mechanical properties of the plastics material.

Of course, rather than applying a vacuum from the outside of thepreform, a positive pressure may be applied (by means of a fluidinjector and lip seals) to the inside of the preform, to cause thepreform to contact at least a portion of the cooling tube insidesurface, although this requires a sealed system. Any appropriatepressure differential may therefore be applied between the insidesurface of the cooling tube and the outside surface of the plastic part,depending on the shape of the part and the cycle time provided for thecooling. It is preferred that the entire outer surface of the preform(cylindrical outer surface and spherical outer surface at the distaltip, i.e. the dome 80) contact the porous insert cooling tube, althoughan outer profile of the preform may, in fact, prevent this along, forexample any inwardly tapering portion 84 proximate the neck finish ofthe preform 32. However, the cooling tube and vacuum structure may bedesigned to bring any portion(s) of the preform into contact with thecooling tube, depending on the plastic part design and the portion(s)thereof needing cooling. Further, the vacuum (or positive pressure) maybe applied in one, two, or three or more stages to effect variouscooling profiles of the plastic part. For example, a thick portion of apreform may be brought into immediate contact with the cooling tube,while a thinner portion of the preform may be brought into contact withthe cooling tube at a later time. In general, the preform is in contactwith the cooling tube 50 for sufficient time only to allow robusthandling of the preform without any fear of damage arising, with thisdependent upon preform material, size and cross-sectional profile.

The porosity of the porous insert 52 can be lowered to improve thesurface finish (i.e. inner surface 82) of the porous insert 52 incontact with the molded plastic part and thereby minimize any marking ofthe molded part's surface. Reducing the porosity of the insert 52 also,however, reduces the flow of air passing therethrough. A modest flowreduction can be tolerated since this does not greatly impede the effectof the vacuum created or diminish its intensity, especially since, oncethe molded part's surface contacts the insert, all airflow ceases. Theairflow rate only affects the speed at which the vacuum is created whenthe molded part 32 initially enters the tube 52. Porosity reduction isachieved by milling and grinding procedures, whereas additional processsteps of stoning or electric discharge can clear debris from surfaceinterstitial spaces to increase porosity. In any event, flow ratethrough the material is a function of both applied pressure andporosity, as will be readily understood.

Inside the cooling tube 50, due to the partially cooled, but stillmalleable, state of the molded part on entry into the molded plasticpart, the vacuum will cause the molded plastic part to expand indiameter and perhaps length. The molded part is subjected to a vacuumapplied to most of its external surface, while its internal surface isexposed to ambient pressure.

In FIG. 5, support ledge 100 of the molded part 32 prevents the partfrom entering further into the tube 50 as the part cools and shrinks. Inthis case, the vacuum draws the closed end of the part further into thetube while the support ledge prevents the opposed end from following. Inall embodiments the vacuum causes the part to change shape tosubstantially eliminate the clearance that initially exists between thepart's outer surface and the corresponding inner surface of the porousinsert 52.

In the case of molded plastic parts having diametric features, such asthe inwardly tapered portion 84, these will not be substantially alteredin shape during this expansion phase. The configuration and size of theinternal dimensions of the porous insert 52 are made such that thediameter matches or is slightly larger than the corresponding diameterof the part being cooled, thus preventing substantial disfiguring of theplastic part shape.

End seal 104 (of FIG. 3) at the open end of the cooling tube 50 providesa means to initially establish (and as necessary maintain) the vacuumwithin the assembly and to continue to cause the part 8. If there aresections of the porous insert 52 that do no engage with portions of thepreform, such as region 106 shown in FIG. 4 below support ledge 100,then the end seal 104 is required to ensure that the molded partsremains in contact with the inner wall 82 and thereby to resist theeffect of shrinkage of the part 8 as it cools, otherwise the end seal104 may be omitted. If the vacuum were not present, shrinkage of thepart 8 would cause a separation between the part's outer wall and theinner cooling wall of the insert 52 (and hence a resulting loss ofsuction), thereby greatly impeding the transfer of heat from the part tothe insert 52 and into the cooling tube. Thus, the continuing provisionof the vacuum ensures intimate contact between the molded part's outersurface and the insert's inner wall 82 is maintained to maximize coolingperformance.

Returning to FIG. 3, the tube assembly 50 is preferably fastened to acarrier or take-out plate 110 by a screw 112. The insert 52 is retainedin the assembly by a collar 114, which is threaded onto the end of thetube body 54 or fastened or otherwise coupled by any other conventionalmeans. A cooling fluid channel inlet 116, and a cooling fluid channeloutlet 118 are provided in the carrier plate 110. A vacuum channel (orpassageway) 120 is also provided in the carrier plate 110. Aftersufficient cooling time has elapsed, the vacuum is replaced withpressurized airflow (by inversion of the vacuum pump function), and thepart is ejected from the tube assembly 50 by this pressure.

FIGS. 5 and 6 show an alternative embodiment for a cooling tube 150 inwhich the tube body 54 and the sleeve are 56 replaced with an extrudedtube that contains integral cooling channels. An aluminum extrusion 152forms the tube body and contains integral cooling channels 154 that arealternately connected to each other by grooves 156 at each end of thetube. Sealing rings 158 close the ends of the tube to complete thecooling circuit's integrity. A porous aluminum insert 160, havingexternal grooves 162 that act as a channel for the vacuum, is located(inside the cooling tube 150) by a spacer 164 and a collar 166 attachedto the tube by a thread or any other conventional fastening mechanism.The tube assembly is fastened to the carrier plate 110 by any suitableexternal clamping means, such as a bolt 168. This alternative embodimenthas a lower cost of manufacture and an improved cooling efficiency byvirtue of its extruded body component.

FIG. 7 shows a second alternative embodiment for cooling a molded parthaving a different shape. In this arrangement, the end seal (referencenumeral 104 of FIG. 3) between the top of the cooling tube and theunderside of the support ledge 100 is not necessary. A porous insert 200is held within the extruded tube 152 by a collar 201 that is threaded202 onto the top of the cooling tube (in this case the extruded tube152) or fastened by any suitable means. The collar 152, typically madefrom aluminum or the like, extends inwardly to conform to the innerprofiled shape 204 of an open end of the insert 200 that matches, or isslightly larger, than that of the part being cooled. The collar 201provides a seal of sufficient efficacy to allow the vacuum applied tothe porous insert to cause the part to expand in size to intimately fitagainst the inner surface of the insert and cool. In some cases it ispreferred that the part has a looser fit in the tube when first enteringit. In this event, FIG. 8 shows how a lip seal 210 can provide thenecessary initial sealing to permit a vacuum to become effective afterthe loading of a looser fitting part.

Methods of constructing and using the cooling tubes (in an operationalenvironment) of the present invention to accentuate cooling and partformation have been described above. Briefly, a porous cooling tubeconstructed in accordance with one of the embodiments of the presentinvention is manufactured by milling or extruding a cooling tubeassembly having a porous cooling tube insert and, optional butpreferable, cooling fluid channels. The porous insert may be polished,painted, or otherwise treated to reduce porosity and provide a finerfinish to the exterior of the molded part. The cooling fluid channelsmay be wholly enclosed inside the tube, or may be formed by placing asleeve over open channels formed in the outer surface of the porousinsert. Vacuum channels may be milled or extruded on an outer surface ofthe porous insert, or may be provided with separate structure adjacentthe porous insert outer surface. The closed end of the cooling tube maybe machined into the tube, or may comprise a plug fitted into one openend of a cooling cylinder. Appropriate seals are then fitted to eitherend of the cooling tube to provide the required pressure management, asdescribed above.

In operation, the just-molded plastic part is extracted from a moldcavity and carried by the carrier plate to a cooling station where oneor a plurality of cooling tubes are positioned. The plastic part isinserted into the cooling tube and preferably sealed therein. Then, avacuum (or partial vacuum) is applied through the porous insert from theouter surface thereof to the inner surface thereof, causing the plasticpart to expand in length and diameter to contact the inner surface ofthe porous insert. The cooling fluid circulates through the coolingchannels, extracting heat from the porous insert, which extracts heatfrom the molded part. When sufficient cooling is complete (when theexterior surfaces of the molded part have solidified and achievedsufficient rigidity), the vacuum is released and the molded part isejected, for example, into a bin for shipping. If desirable, a positivepressure can be applied through the vacuum channels to force the moldedpart from the cooling tube.

Thus, what has been described is a novel cooling tube assembly for theimproved cooling of partially cooled molded parts that provides a meansto maintain intimate surface contact between the part's external surfaceand the internal cooled surface of the tube during the cooling cycle.The disclosed post mold cooling device preferably uses a vacuum toslightly expand the part to contact the cooled surface and to maintaincontact as part cools, thereby counteracting shrinkage that tends todraw the part away from the cooled surface.

All U.S. and foreign patent documents, and articles, discussed above arehereby incorporated by reference into the Detailed Description of thePreferred Embodiment.

The individual components shown in outline or designated by blocks inthe attached Drawings are all well-known in the injection molding arts,and their specific construction and operation are not critical to theoperation or best mode for carrying out the invention.

While the present invention has been described with respect to what ispresently considered to be the preferred embodiments, it is to beunderstood that the invention is not limited to the disclosedembodiments. To the contrary, the invention is intended to cover variousmodifications and equivalent arrangements included within the spirit andscope of the appended claims. For example, whilst the preferredembodiment of the present invention discusses the present invention interms of a porous insert, it will be appreciated that the insert could,in fact, be realized by a thermally conductive but porous coatingapplied to a profiled housing, although use of an insert benefits easeof manufacture and assembly. The application of the cooling technologyis not, as will be understood, limited to size or weight (of, e.g.preforms), with the defining criteria being the ability to establish avacuum to encourage contact of an outer surface of the molded articlewith the inner surface of the porous profiled substrate. The scope ofthe following claims is to be accorded the broadest interpretation so asto encompass all such modifications and equivalent structures andfunctions.

1. A post-injection-molding cooling apparatus configured to cooperatewith a vacuum structure said vacuum structure capable of cooling ajust-injection-molded malleable injection molded plastic articlereceived within the cooling apparatus said apparatus, comprising: aporous member formed from a porous material, the porous member including(i) an inside surface that is profiled to substantially reflect a shapeof a portion of an outside surface of the injection-molded plasticarticle, and (ii) a vacuum coupling structure; wherein the vacuumcoupling structure of the porous member is configured to cooperate withthe vacuum structure to provide a reduced pressure adjacent the insidesurface of the porous member to cause the portion of the outside surfaceof the malleable molded plastic article to contact the inside surface ofthe porous member so as to cause a conductive cooling of the outsidesurface of the malleable article.
 2. The cooling apparatus of claim 1,wherein the vacuum coupling structure comprises an outside surface ofthe porous member.
 3. The cooling apparatus of claim 1, wherein thevacuum coupling structure comprises at least one channel formed in anoutside surface of the porous member.
 4. The cooling apparatus of claim1, wherein at least a portion of an outer surface of the porous membercomprises a mounting surface configured to connect with an insidesurface of a cooling tube.
 5. The cooling apparatus of claim 1, furtherconfigured to cooperate with a plug for providing a closed end to theprofile of the inside surface of the porous member, the plug beingshaped to correspond to a domed end portion of the molded plasticarticle.
 6. The cooling apparatus of claim 3, further comprising atleast one vacuum channel configured to be coupled to the at least onechannel formed in an outside surface of the porous member.
 7. Thecooling apparatus of claim 1, wherein the inside surface of the porousmember includes a closed end that is shaped to correspond to a domed endportion of the molded plastic article.
 8. The cooling apparatus of claim7, wherein the porous member further includes a channel extendingtherethrough at a base of the closed end thereof, the channel beingconfigured to be connected to a low pressure, source to draw the moldedplastic article into the tube assembly.
 9. The cooling apparatus ofclaim 1, wherein the porous member has porosity in the range of about3-20 microns.
 10. The cooling apparatus of claim 1, wherein the porousmember comprises a porous aluminum.
 11. The cooling apparatus of claim1, further including a cooling structure configured for connection witha heat dissipation path, for cooling the molded plastic article incontact with the inside surface of the porous member.
 12. A device forreceiving and cooling a just-injection-molded semi-molten plasticarticle, the cooling device comprising: a porous member having (i) aninternal surface configured to receive the semi-molten article, and (ii)an external surface; wherein the porous member is configured such thatthe just-injection-molded semi-molten article is moved substantiallyagainst the internal surface by a pressure differential between theexternal surface and the internal surface.
 13. The device according toclaim 12, further comprising low pressure structure for applying thepressure differential between the external surface and the semi-moltenarticle.
 14. The device according to claim 12, wherein the porous memberis configured as a removable insert to be removable from an injectionmolding tube assembly.
 15. An apparatus for use in a post mold device,said apparatus capable of vacuum-forming of a just-molded malleableinjection molded plastic article, comprising: a tubular porous memberconfigured to be removably installed within the post mold device, thetubular porous member having (i) a porous inside surface that isprofiled to substantially reflect at least a portion of an outsidesurface of the molded plastic article, and (ii) a porous outsidesurface, the porous inside surface and the porous outside surface beingconfigured to provide a pressure differential therebetween to cause anonsolid molded plastic article within the porous member to contact atleast a portion of the porous member inside surface so that a profile ofthe molded plastic article reflects a profile of the porous memberinside surface.
 16. The apparatus according to claim 15, furthercomprising a channel configured to provide low pressure to the tubularporous member outside surface.
 17. The apparatus according to claim 15,further comprising a vacuum device, coupled to the channel, to causeboth (i) an exterior cylindrical surface of the molded plastic articleand (ii) an exterior distal end of the molded plastic article to contactthe interior surface of the porous member.
 18. A forming apparatusconfigured to cooperate with an evacuation pump for the vacuum-formingof a just-molded malleable injection molded plastic article, comprising:a porous member having a porous inside surface that is profiled tosubstantially reflect at least a portion of an outside surface of themolded plastic article and that supports the evacuation of airtherethrough to cause the malleable molded article within the at leastone porous member to expand to contact the porous inside surface tocause a substantial portion of the outside surface of the malleablearticle, upon cooling, to attain a profile substantially correspondingto the profile of the inside surface of the porous member.
 19. A toolconfigured to be carried by an injection molding robot arm, comprising:a carrier configured to be coupled to the injection molding robot arm,said carrier carrying at least one molded article cooling device; atleast one porous member installed in the at least one molded articlecooling device, the at least one porous member having a porous insidesurface that supports the evacuation of air therethrough to cause amalleable molded article within the at least one porous member to expandto contact the porous inside surface; and an evacuation structureconfigured to evacuate the air through the at least one porous member.20. An injection mold robot, comprising: an arm member configured to bedisposed adjacent an injection molding machine; a carrier configured tobe coupled to the arm member, said carrier carrying at least one moldedarticle cooling device; at least one porous member configured to beremovably installed in the at least one molded article cooling device,the at least one porous member having a porous inside surface thatsupports the evacuation of air therethrough to cause a malleable moldedarticle within the at least one porous member to expand to contact theporous inside surface; and an evacuation structure configured toevacuate the air through the at least one porous member.
 21. Aninjection molding machine, comprising: mold structure that molds atleast one plastic article; at least one cooling cavity configured tohold and cool the at least one plastic article after the at least oneplastic article is molded by the mold structure; at least one porousmember configured to be removably installed in the at least one coolingcavity, the at least one porous member having a porous inside surfacethat supports the evacuation of air therethrough to cause a non-solidmolded plastic article within the at least one porous member to expandand contact the at least one porous member inside surface, a profile ofthe molded plastic article corresponding to a profile of the porousmember inside surface; and an evacuation structure configured toevacuate the air through the at least one porous member.